This invention is a method for the recovery of waste heat from smokepipes, chimneys or stacks using natural draft. All the prior art known to me suffers from the natural limitation that only a fraction of the stack heat can be recovered lest the natural draft be hopelessly impaired. Countless arrangements have been devised to nibble away some of that heat but all have been remiss in identifying the nature of the problem and have been accepting stack heat losses as an inevitable price to pay for draft--when actually we can regain it all.